1. Field of the Invention
The present invention relates to a condenser microphone and a method of manufacturing the same, and more particularly, to a micromini condenser microphone having a flexure hinge diaphragm and a method of manufacturing the same.
This work was supported by the IT R&D program of Ministry of Information and Communication/Institute for Information Technology Advancement [2006-S-006-01, Components/Module technology for Ubiquitous Terminals.]
2. Discussion of Related Art
Generally, a condenser microphone uses a principle in which a change in capacitance caused by vibration of a diaphragm due to external vibration sound pressure is output into an electrical signal, which can be applied to a microphone, a telephone, a mobile phone and a video tape recorder.
FIG. 1A is a cross-sectional view of a conventional condenser microphone having a disk-shaped diaphragm, and FIG. 1B is a cross-sectional view of a conventional condenser microphone having a pleated diaphragm.
Referring to FIGS. 1A and 1B, the conventional condenser microphone includes a silicon wafer 11, a back plate 12 formed on the silicon wafer 11, and a diaphragm 14 disposed on the back plate 12 with an air gap 13 interposed therebetween. A plurality of sound holes 12a passing through the back plate 12 and in communication with the air gap 13 are formed, and an insulating layer 16 is formed between the back plate 12 and the diaphragms 14 and 15.
The diaphragm 14 illustrated in FIG. 1A has a disk-shape, and the diaphragm 15 illustrated in FIG. 1B has a pleated structure. Generally, the flexible diaphragms 14 and 15 may be formed to be easily vibrated by minor external vibration and to improve the sensitivity of a microphone, and thus a conventional diaphragm may be formed in a disk-shape or pleated structure to obtain mechanical flexibility.
However, the condenser microphone having the above-described structure may need an energy higher than a certain level to sufficiently vibrate the diaphragm, so the pleated diaphragm 15 illustrated in FIG. 1B may be formed rather than the disk-shaped diaphragm 14 illustrated in FIG. 1A, thereby enhancing flexibility of the diaphragm. However, sufficient sound pressure has to be input to vibrate the diaphragms of these condenser microphones.
Moreover, the conventional condenser microphones having the conventional structure described above have poor performance in a low frequency range when scaled-down to 1 mm or less using a semiconductor MEMS process. Also, general frequency response characteristics of the condenser microphone exhibit high sensitivity in a low frequency range when the area of the diaphragm is large, and low sensitivity in a high frequency range when the area of the diaphragm is small.